This invention relates to an improved freight railcar truck and more particularly is directed to an improved truck bolster having distal ends that extend outward of the truck side frames to support the weight of a carbody at its side sills.
Although there are other designs for freight railcar trucks, the vast preponderance of freight car trucks in domestic U.S. service are known as three piece outboard bearing trucks. That is to say the truck comprises three principal parts, namely a floating truck bolster laterally connecting two side frames; and the side frames are mounted on two wheelsets each including two flanged wheels mounted on an axle. The truck bolster is spring supported on what is commonly referred to as a "secondary suspension" system for vertical cushioning movement on the side frames. Bearings are mounted on the axles adjacent each wheel and the ends of each side frame are primarily suspended between corresponding bearings on the two axles. In freight car truck construction there is no significant vertical spring movement of the primary suspension. Where the bearings and side frames are located outboard of the wheels, the truck is referred to as outboard bearing.
In most rail car assemblies two trucks are required, one at each car end, and the car under frame includes longitudinal side sills and transverse body bolsters, the latter being located directly above the truck bolsters and serving to transfer the car load to center bearing plates (or bowls) at the geometric center of the truck bolsters. There is usually also a center sill at the ends of the rail car intersecting the body bolsters which center sills contain coupling gear and serve to transmit longitudinal draft and buff forces to the car body bolster and thence to the truck bolster.
Examples of other rail car truck designs may be found in the following United States patents:
I. Rail car trucks connecting the car body directly to the truck side frame:
Ser. No. 516,935 springs extend directly above the side frames to support the car body without a truck bolster; PA1 Ser. No. 900,760 springs extend directly upwardly from each side frame to the car body and a truck crosspiece is rigidly fastened to both side frames; PA1 U.S. Pat. No. 2,011,918 springs support each side frame on axles outboard of the wheels with rigid cross beams between the side frames, and the car body sits on rollers carried by the side frames; and PA1 U.S. Pat. No. 3,961,584 springs supporting the car body extend upward from side frames that are bolted to a horizontal cross plate. PA1 Ser. No. 731,626 a passenger car body is supported on springs carried on a second transverse beam outboard of side frames that are otherwise connected by a truck bolster (a second embodiment for freight cars supports the car body on springs seated on a truck bolster inboard of the wheels); PA1 U.S. Pat. No. 1,211,789 levers pivotally mounted on side frames support the car body on structures inward of the side sills; PA1 U.S. Pat. No. 4,237,791 an inboard bearing truck has a bolster that carries car supporting pneumatic springs outboard of the wheels. PA1 U.S. Pat. No. 2,046,391 an inboard bearing truck supports the car body on a bolster centerplate and has auxiliary roller type side bearings on ends of the bolster outboard of the wheels.
II. Rail car trucks supporting the car body upon bolster ends outboard of the side frames:
III. Other:
From the foregoing prior art and other knowledge of the railroad industry it can be ascertained that freight car construction, as contrasted to passenger car construction, favors a minimum of truck parts and simplified suspension systems so as to reliably carry heavy loads at minimum operating expense and low original equipment cost. Simplicity of design with minimum weight and number of parts will usually contribute toward those goals. Additionally the industry seeks rail car dynamic stability for operating safety; and efforts to lower a car center of gravity and to reduce car roll will contribute toward that goal.